Structural Analysis of a Metazoan Nuclear Pore Complex Reveals a Fused Concentric Ring Architecture
Structural Analysis of a Metazoan Nuclear Pore Complex Reveals a Fused Concentric Ring Architecture
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DOI：
10.1016/j.jmb.2009.11.010
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发表时间：
2010-01-22
影响因子：
5.6
通讯作者：
Medalia, Ohad
中科院分区：
文献类型：
--
作者：
Frenkiel-Krispin, Daphna;Maco, Bohumil;Medalia, Ohad
细胞质和细胞核之间分子交换的唯一通道是核孔复合体（NPC）。这种大的超分子组装体介导货物进出细胞核的运输，并融合内外核膜以形成水性易位通道。NPC由8个蛋白质不对称单位组成，形成假8倍对称通道。由于其剪切尺寸、复杂性和塑性性质，解剖NPC在其水合状态下的高分辨率三维结构是一个艰巨的挑战。为了实现这一目标，我们应用冷冻电子断层扫描从非洲爪蟾卵母细胞的核膜传播。为了补偿单个NPC的8重对称性的扰动，我们对三维层析NPC体积进行了独立于几何的非对称单元平均，最终得到了6.4 nm分辨率的精细模型。这种方法揭示了新的结构特征，特别是在辐条环复合物和管腔域。沿着易位通道发现辐环复合物的稠合同心环结构。此外，精制的爪蟾模型的比较，其Dictyosteoprotein同系物产生类似的孔径在三个典型的环的水平，虽然爪蟾NPC被发现是30%高于Dictyosteoprotein孔。这种差异主要归因于与脊椎动物相比，网骨藻基因组中一些核孔蛋白的同源性相对较低和组织不同。然而，实验条件施加一个优选的轴向方向的NPC内传播非洲爪蟾卵母细胞核膜。这可以至少部分地解释增加的高度重建脊椎动物的NPC相比，从完整的网骨细胞核的断层重建。(C)2009爱思唯尔有限公司保留所有权利。
The sole gateway for molecular exchange between the cytoplasm and the nucleus is the nuclear pore complex (NPC). This large supramolecular assembly mediates transport of cargo into and out of the nucleus and fuse the inner and outer nuclear membranes to form an aqueous translocation channel. The NPC is composed of eight proteinaceous asymmetric units, forming a pseudo-8-fold symmetric passage. Due to its shear size, complexity, and plastic nature, dissecting the high-resolution three-dimensional structure of the NPC in its hydrated state is a formidable challenge. Toward this goal, we applied cryo-electron tomography to spread nuclear envelopes from Xenopus oocytes. To compensate for perturbations of the 8-fold symmetry of individual NPCs, we performed symmetry-independent asymmetric unit averaging of three-dimensional tomographic NPC volumes to eventually yield a refined model at 6.4 nm resolution. This approach revealed novel structural features, particularly in the spoke-ring complex and luminal domains. Fused concentric ring architecture of the spoke-ring complex was found along the translocation channel. Additionally, a comparison of the refined Xenopus model to that of its Dictyostelium homologue yielded similar pore diameters at the level of the three canonical rings, although the Xenopus NPC was found to be 30% taller than the Dictyostelium pore. This discrepancy is attributed primarily to the relatively low homology and different organization of some nucleoporins in the Dictyostelium genome as compared to that of vertebrates. Nevertheless, the experimental conditions impose a preferred axial orientation of the NPCs within spread Xenopus oocyte nuclear envelopes. This may at least in part explain the increased height of the reconstructed vertebrate NPCs compared to those obtained from tomographic reconstruction of intact Dictyostelium nuclei. (C) 2009 Elsevier Ltd. All rights reserved.